Automatic telephone system



Ame 14,1921.. 1,632,025

cs. E. Dus-NN 4 AUTOMATIC TELEPHONE SYSTEM I Filed Oct. 24 /a I 7 L@ llljf Patented June 14, 1927.

N UNITED STATES N PATENT oFFlcia.i

GEORGE E. DUSTIN, OF WOODCLIFF, NEW JERSEY, .ASSIGNOR TO AMERICANTELE- lPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW-YORK..V

AUTOMATIC TELEPHONE SYSTEM.

Application filed October 24, 1923. Serial No. 670,557.

This invention relates to automatic telephone systems, and more particularly to large multi-office automatic systems.

lts Objectis the provision of an improved trunking arrangement for an automatic telephone system in which connections are established through the medium of serially rela-t-edautomatic switches, and in which one of the switches in a series belonging` to a major groupv of the system may be omitted to this selector whereupon it automatically hunts for an idle trunk.- Thus, the lines in a given group may be reached by means of a smaller seriesof switches than the lines in other groups. v i

Other features will appear from the detailed description.

In the drawings, Figure 1 isa schematic diagram of the trunking system; Fig. 2 is a circuit diagram of a selector arranged to absorb the second digit dialed into it irre spective of the level selected, and Fig. 3 is a circuit diagram of a selector' arranged to absorb the second digit dialed into it on certain specified levels only. f

Fig. 1 showsthe organization of a trunking system as appli-ed to an automatic telephone system having an ultimate capacity of one hundred thousandlines. In a system of this size, the lines are usually distributed among a plurality of different offices, and the first selectors, which are the switches which respond to the first digitin called telephoneV numbers, may function as oice selectors.

Since there are ten levels in a selector switch,

there may be ten different offices and when a callingsubscriber operates his dial to call the desired number, the first digit will operate the first or office selector to select the trunk line leading to the proper office and the remaining digits will operate 'a' seconder incomingl selector 14, a third selector 15, and a connector 16, in the selected office, to com` plete lthe connection. l

Considering Fig. 1 in conjunction with Fig. 3, the office which is reached when the first digit dialed is 2 as well as the *other voffices in the system with the exception ofthe one which is reached when the firstdigit dialed is 3, may be equipped to their full capacity, while for the purpose of illu`stration, it, will be assumed thatrthe office to which the connection is extended `when 3 is the first digit dialed, has for the time being no more than one thousand telephone lines terminating in it.`

. yIn order to point out the trunking arrangement more clearly, it will be assumed that the subscriber at substation 10 (Fig: 1) desires to call the subscriber at substation 17,

A in whichl case, the connection may be extend! edas follows: fromthe substation 10 by wayv of the individual line switch 11, first or office selector 12, second Vorl incoming selector 14, third or hundreds selector 15,and the connector 16 to the substation 17. This, it will be noted, is the usual trunking arrangement. Assuming, now thatthe subscriber at substation 10 calls the subscriber at the substation 7, the connection may betraced as follows: from the substation 10 by way of the rindividual line switch l1, first selector 12,

third or incoming selector 13, and the .con-

nector 18, tothe substation ,7. This latter connect-ion extends over a path similar to the one for thesubstation 17, except that it does not pass through any second or thousands selector such as 14. It is obvious in View of the fact that there is only one thousands group of lines terminating in that office that no thousands selector is needed. Now, it is only necessary to introduce an yextra but in effective digit into the number dialed, tok

make the telephonenumbers in this office have the same numberof digits as those in 'the other offices. This is accomplished inthe system disclosed herein, by arranging the se-A lector 12 so that it will not commence to trunk hunt after initiating the primary or vertical movement when the first digit dialed is 3 until after the second digit irrespective of what it may be, is dialed and. cancelled,

when the selector 12 proceeds to trunk hunt ,in the manner well-known in the art. v

The apparatus having been thus described 4 in a more or less gen-eral manner, its operation will now be described in greater detail. For this purpose it will be assumed that the subscriber atfsubstation 10 (Fig. 1) desires to talk with the subscriber at substation 7, in which case, the second digit will need to be absorbed. `Vhen the receiver is removed at substation 10, the individual line switch 11 is operated to extend the connection to an idle first or oiiice selector 12 in the manner well-known in the art. Assumin@- that a digit absorbing selector of the type snown in Fig. 3 is the selector 12 in Fig. 1 which the connection is extended, the following circuit is closed to operate relay 300: battery, right winding of relay 300, 374, 375, 308, subscribers line and instrument, 307, 372, 371, left windingV of relay 300 to ground. Relay 300 operates and closes a circuit to operate relay 310 as follows: battery, relay 310, 303, 302, 381, 380 to ground. Relay 310 connects ground to lead 309, to cause the selector to test busy to other line switches over a circuit follows: ground 312, 311 to lead 309. The selector switch is now ready to receive the first series of impulses set up by the subscribers calling device, which series ordinarily in a` multi-oilice district, corresponds to the office code of the number dialed, and relay 300 follows the impulses. When relay 300 releases on the first break in the line, a circuit is closed to operate relay 320 as follows: battery, relay 32o, :515, aia, aol, ses, ssi, sse to ground. The primary or vertical magnet 341 also operates in parallel with relay 320 by way of 331 and 332. Relays 31.0 and 320 are made slow-to-release, to prevent them from releasing when relay 300 opens alternately,

their respective holding paths during the impulse period, but the vertical magnet 341 follows the impulses set up by relay 300. The first time the vertical magnet 341 operates it raises the selector rod 390 of which only a part is shown, sufficiently to close the contacts 391 and 392, 393 and 394, and 395 and 396, thus preparing a circuit whose function is hereinafter described. Each time the vertical magnet 341 operates, the selector rod 390 carrying the brushes 327, 328 and 329 is raised one step in the manner well-known in the art, until, when the impulses cease the brushes 327, 328 and 329 are in the proper position to engage with the terminals of the first trunk in the selected level, as soon as the rot-ary magnet 342 operates as hereinafter described. TWhen the series of impulses ceases relay 300 remains energized and opens at 302 the circuit through relay 320 which releases. lVhen relay 320 releases Aa circuit is closed to operat-e relay 330 as follows: battery, relay 330, 362, 357, 394, 393, 322, 321, 326, 311, 312 to ground. Relay 330 operated, locks as follows: battery, relay 330,392, 391, 343, 344, 337, 336, 381, 380 to ground. Relay 330 Aoperated, disconnects at 331 the vertical magnet 341 from the circuit. The selector switch is now ready to receive the series of impulses ordinarily corresponding to the thousands digit of the number dialed, but which, in the present case, will be absorbed.

rEhe neXt series of impulses, 3 in number, corresponding to the thousands digit is now dialed and relay 300 follows the impulses as before, operating relay 320 in the manner previously described. Relay 350 also operates in parallel with relay 320 over a circuit as follows: battery, left winding of reny 354, ses, sul, ses, 381, 380 to ground. Relay 350 operated locks as follows: battery, left winding of relay 350, 355, 353, 311, 312 to ground. Relay 320 operates before relay 350, thus disconnecting the rotary magnet 342 from the circuit to prevent it from operating prematurely. taince the relay 320 remains operated during the impulse period and since the rotary magnet 342 cannot operate while relay 320 is operated, the second series of impulses will be dissipated before relay 320 releases and it is therefore apparent, that the second series of impulses will be rendered ineffective before relay v320 releases and permits the rotary magnet 342 to trunk hunt. lhen the second series of impulses ceases, relay 320 releases as previously described and closes a circuit to operate the rotary magnet 342 as follows: battery, rotary magnet 342, 33 335, 356, 357, 394, 393, 322, 321, 326, 311, 312

to ground. The rotary magnet 342 operated opens at 343 the holding circuit through relay 330, and causes the selector rod 390 to rotate and advance the brushes 327, 328 and 329, to the terminals ofthe rst trunk in the level selected. group selected is busy, ground will be present on terminal 339, and when the rotary magnet 342 releases, a circuit will be closed to re-operate relay 330 as follows: battery, relay aso, 392, ser, 34a, 344, see, sci, 379, 378, 319, 329 to ground. Relay 330 operated, closes the circuit previously described to operate rotary magnet 342, thus causing relay 330 to release and the selector rod 390 to rotate another step and carry brushes 327, 328 and 329 to the terminals associated with the next trunk in the group. This cycle of operations continues until an idle trunk is found. lVhen an idle trunk is found, ground will not be connected to brush 329. Hence, relay 330 will not operate, but a circuit will be closed to operate relay 370 as follows: battery, relay 330, 392,391, 343, 344, 360, 361, 370, 311, 312 to ground. Relay 370 has been previously shunted out by ground at 329 or 380. Due to the high re` sistance of relay 370v relay 330 will not operate. vRelay 370 operated releases relay 300; connects lead 307 to brush 327 by way of 372, 373, and 317; lead 308 to brush 328 1f the first trunk in the,

by way of 375, 376, and `318; and lead 309 to brush` 329 by way of 377, 378 and 319. The calling subscribers line is now extended by way of brushes 327 and 328 to a selector such as the selector 13 shown in Figure 1, and ground from selector 13 is connected to brush 329 by way of terminal 339. Relay 370 now locks over the following circuit:

battery, relay 330, 392, 391, 343, 344, 330,'

leased, releases relay 310 but the latter being slow-to-release, Willremainoperated `long enough for relay 370 to lock before its operating circuit is opened at 311 by the release of relay 310. 1 ,Y

y The circuit will be extended to the called station 7 (Fig. 1) by means of other selector Switches such las the selector 13 and connector 18 in the manner well-known in the art.

Y l/Vhen the receiver is replaced on the switchhook. at the 'l calling subscribers station, ground will be removed from the brush 329 andrrelays 350 and 370 will release and the release magnet 340 'will operate as lfollowszbattery, release magnet 340, y396, 395, 313, 314, 301, 302, 381, 380 to ground. When the release magnet 340 operates the selector rod 390 releases and restores to normal, thus opening at 396 the circuit through the release magnet 340,'Which releases.

It will vnow be assumed that the subscriber at substation 10 (Fig. 1) 'desires to talk with the subscriber at substation 17 in whichcase the first digit dialed is the ,digit 2 and the second digit dialed must notbe absorbed.

Whenthe receiver is removed at substation 10 (Fig. 1), the individual line .switch 11 s operated to extend the'connectio'n lto the selector switch 12 as before.' The first series of impulses is dialed, 'and relays 300,l 310, 320 and the vertical magnet 341, operate and function in` the manner previously described. When the firstlseries of impulses ceases, re-A la'y 320 releases, and closes the circuits previously described, to operate and lock relay 330.y Assuming that thedigit 2 was the first digit dialed, the vertical magnet 341 will have operated twice and raised the selector rod 390 carrying the brushes 327, 328, 329 and 345 two steps, so that the brushes 327, 328 and 329 will bein a position to engage the terminals of the iirst trunk inthe second level, when the` rotary magnet 342 operates,

as hereinafter described. yThe brush 3454 will alsobe resting upon contact-346 yof the commut-ator. A'circuit will now b 'e closed as follows to operate relayl 350:` battery,ro tary magnet 342', 334, 335, 353, 359, 34:6, 3,45., left winding of relay 350y to ground.l "Due to the high resistance ofithe Windingjofrein effect under these conditions, merely performingv the function required of the standard selector-"ordinarily used inthe Stro'wger system, and is not called npon to cancel the seconddigit by rendering it ineffective;

The selectorjswitch shown in Fig. 2 is. a

- modification of the circuit shown in Fig.3.

This selector switch absorb-s the second digit dialed into it irrespective of its character.

In asystem such as is shown inFig. 1 if a digit absorbing selectorof this type were used itwould necessarily be substituted for the selector switch 13, anda standard selector switch would inA` such `casebe used in place of the first-or iceselector v12.

Considering Fig. 2 in conjunction. with Fig. 1 let usr assumethat the calling fsub-' scribers station 10 (Figpl) desires to call the substation 7, then when the circuit from the calling station 10 is extended by wayof theline switch 11, and a standard selector, to the digit'ab'sorbing selector 13 (Figf2), a circuit to operate relay 200 will `be closed over leads `207 and208. Relay 210 will op-- erate and connect ground to le'ad`f209 by wayV of 211 and y'212,fto cause the selector to`test busy to other first selectors.

theve'rticalmagnet 241 being in parallel, will 'operatewhen relay 200 releases dur` ing vthe impulse period, land the selector -rod 290 carrying the brushes 227, 228 and 229, will advance until the brushesfare opposite thelevel selected. `When' theimpulses cease relay 220y releases, closing the'circuit to operte relay ,i230 as follows battery, relay 230, 257, 256,293, 294,222, 221, *226, 211, 212 to ground. Relay `230 operated locks aspfollows: battery, relay 230, 292, 291, 243,244,"

slow relay 220 i 237, 23e, 231-230 to ground. 'Reny 25o is now connected in parallel with relay '220, by

way of 233.".and 232 sov that when the next` series ofimpulses dialed and` relay 200 periodically releases, relays 220 vand 250 willfboth operate. Relay 250' operated,-

`locks to` ground at V-211 and 212. The cir-v cuit to operate" thefrotary magnetf242 isA 211,212to ground.'` .Thusv it is evident that since the rotary magnet 242 was prevented from operating until after the impulses corresponding to kthe second digit dialed into the selector had ceased, such second digit was rendered ineffective and thereby cancelled.

From this point the selector will hunt for an idle trunk as described in connection with Fig. 3. The connection will be extended to the connector 18 and substation 7 in the manner well-known in the art. When the calling station receiver is replaced on the switchlioolr, relay 270 releases, closing the circuit to operate the release magnet 240 and the selector switch is restored to normal in the well-known manner. Y Vhile the digit absorbing selectors show in Figs. 2 and 3, have for purposes of illustration, been respectively used as an incoming selector and an oiiice selector, they are not so limited but may be substituted for any selector switch of a series in an automatic telephone system as conditions may dictate.

lVhat is claimed is:

1. In combination, a telephone line, an automatic switch, means for extending the line to said switch, means for sending a series of impulses to operate said switch to further extend said line, and means in said switch for absorbing the next series of impulses transmitted thereto.

2, In combination, an automatic selector switch, trunks Vterminating therein, an impulse sender, a circuit including said switch and sender for directively operating said switch in accordance with a series of impulses, means in said switch for rendering ineffective the next set of impulses while maintaining said switch in its set position, and means thereupon automatically operated for causing said switch to select an idle trunk.

3. In an automatic telephone system, a calling line equipped with a calling device, a lirst selector, second selectors, and connectors responsive toy impulses set up by said calling device,`each selector switch having both a primary and a secondary movement, groups of telephone lines, one of said groups being reached from saidriirst line via said first selector a second selector and a connector, certain others of said groups being reached from said iirst line viapsaid iirst selector, a second selector, a third selector' and a connector, all oi the lines aforesaid being designated by telephone numbers having the same number of digits, and means for preventing said first selector from moving oli normal in a secondary movement until after receiving'a second series 'of impulses dialed into it from saidy calling device whenever a telephone line -reached via said iirst mentioned second selector is called.

4. In a multi-office automatic telephone system, a calling line equipped with a calling device terminating in a lirst oiice, a second telephone line terminating in a seeond oiiice, a third telephone line terminating in a third oiiice, all ot' said telephone lines being designated by telephone numbers having the same number of digits, a first selector in said iirst ofiice, a series of switches in the second oii'ice operable to connect said calling telephone line with the said second line via said first selector, another series 0fv s vitches in the third ol'lice operable to connect said calling line with the third telephone line via said .lirst selector, said latter series of switches being great-er by one than the former series, each selector switch having both a primary and secondary movement, and means :t'or preventing said lirst selector from .moving oil normal in a secondary movement until after receiving a second series ofV impulses dialed into it from said calling device whenever a telephone line in said second oiiice is called.

rIn a digit absorbing selector having a primary movement in response to a series of in'ipulses,and an autoiuatic secondary movenient, an oil-normal spring, an impulse relay, a fast relay, a slow to operate relay, a slow release relay, and au electromagnet in eombiinition, a circuit to operate said fast relay under control oi said contact spring and said slow release relay, a circuit to operate said slow to operate relay under control oi said tast relay and said impulse relay, and a circuit controlling said electromagnet under control of said fast relay and said slow to operate relay to prevent said eleetromagnet from initiating the secondary movement of said selector switch until after a second series of impulses has been received. 6. In a telephone system, a selector switch, means responsive to impulses for operatin thevsame, said switch having primary an secondary selecting movements, an electromagnet, a double wound relay, a slow relay energized during the rst impulse period and deenergized at the completion thereof to energize said double wound relay at the completion ofthe iirst impulse period on certain levels, and during the second impulse period on other levels, and a circuit controlled by said double wound relay `for e11- ergizing said electromagnet to initiate the secondary movement of said selector switch, in order to absorb or utilize at will a particular series of impulses.

7. In a telephone system, a selector switch responsive to impulses, said switch having primary and secondary selectivemovements, a fast relay, a slow release delay energized during the primary movement and deenergized onthe completion thereof to operate said fast relay, a slow to operate relay under control of said Vtast relay in combination with said slow release relay, an electromagnet, and a circuit for said electromagnet so controlled by the relays aforesaid in combination as to prevent said electromagnet from initiating the secondary movement of said selector switch until a second series of impulses have been received, in order to cancel one of the digits in the number without releasing the selector switch.

8. In a telephone system, serially related groups of automatic switches responsive to impulses,` and means comprising circuit arangeinents in each switch of. one or more groups for preventing a secondary movement of said switch on one or more levels until after a second series of impulses has been received by said switch.

9. In combination, a telephone line, a se-V ries of automatic switches,y means for extending the-line to said switches, means for sending a series of impulses to operate a certain one of said switches for the ypurpose of further extending said line tothe succeeding switch, means in said certain switch for absorbing the next series of impulses trans# mitted thereto, and means effective following the absorption of said series of impulses for transmitting succeeding series of impulses to operate the succeeding switches. In testimony whereof,'I have signed m name to this specification this 22nd day of October 1923. f GEORGE E. DUSTIN. 

